Unveiling the Viral Landscape in Gastric Cancer.

The present study aimed to comprehensively characterize the cancer-associated virome in patients with gastric cancer. A total of 452 samples were analyzed, including 226 tumor tissues and 202 peritumoral tissues from patients undergoing surgical resection, alongside 24 normal gastric mucosa samples obtained via endoscopy from individuals without cancer. RNA was extracted, libraries were prepared, and paired-end sequencing was performed on the NextSeq 500 platform (Illumina, US). High-quality reads were processed with Kraken2, using the standard database supplemented with the Reference Viral Database, to identify viral taxa. Taxonomic profiles, differential viral abundance, and alpha and beta diversity metrics were computed in RStudio, with statistical analyses performed to compare viral composition and diversity among tissue groups using Kruskal-Wallis, Wilcoxon, PERMANOVA, and PERMDISP tests (p < 0.05). Across all gastric tissues, 47 viral orders and 637 viral genera were detected, of which only 10.6% were shared among tissue types, suggesting low conservation and instability of the gastric virome. Gastric tumors exhibited high relative abundance of bacteriophages and clinically relevant eukaryotic viruses, along with reduced viral richness and diversity and marked heterogeneity among tumors. Overall, this study reveals tissue-specific and heterogeneous viral communities, with tumors showing reduced diversity among rare taxa while dominant viruses remain stable, highlighting ecological instability, patient-specific virome reorganization, and the potential of the gastric virome as a biomarker and target for tumor-virome studies.